What do you mean "unofficial"?
We mean that this site is not affiliated with the Prototype Core team or Thomas Fuchs. They are not responsible for its content, so if you see something here that's wrong or that you don't like, don't give them a hard time about it. Give us a hard time about it — or better yet, pitch in and help!
So where's the official stuff then?
The official Prototype site is http://prototypejs.org
The official script.aculo.us site is http://script.aculo.us; there's even an official wiki
The official end-users' discussion group for Prototype & script.aculo.us is this Google Group